Scar Sarcoidosis: A Retrospective Investigation into Its Peculiar Clinicopathologic Presentation

BACKGROUND: Scar sarcoidosis (SS), a rare form of cutaneous sarcoidosis, develops from pre-existing scars. Owing to its rarity, the clinicopathologic features and its significance in clinical prognosis have been obscure. OBJECTIVE: This study aimed to investigate clinical, laboratory and histopathologic findings and to clarify characteristics associated with the development of SS and systemic involvement. METHODS: We retrospectively assessed clinical, laboratory and histopathologic findings of SS. Clinical factors including demographics, anatomic area, number of lesion (single, multiple), presence of symptoms, latent period, injury types related to scar and the proportion of systemic involvement were investigated. RESULTS: Of the 21 patients with SS, skin lesions appeared predominantly in females (85.7%) and in the head and neck (57.1%). The mean latent period was 163.5 months and 13 patients (61.9%) had multiple lesions. Injury types were varied, with no specific type identified as associated with SS. Histologically, discrete sarcoidal granulomas surrounded by densely packed collagen bundles with a thickening of numerous fibers were observed. Ten patients (47.6%) had systemic involvement and showed significantly more of the multiple lesions, longer latent period and higher level of mean serum angiotensin-converting enzyme than those without systemic involvement. CONCLUSION: Various causes of scar were related to SS, but no specific injury type was identified as leading to SS. Although the exact pathomechanism remains unclear, the possibility of systemic involvement could be considered when the patients have multiple lesions, longstanding scars, and elevated serum angiotensin-converting enzyme.